Mirror unit

ABSTRACT

A mirror unit includes an optical scanning device, a frame member, and a window member. The frame member includes first and second wall portions facing each other in an X-axis direction. The first wall portion is higher than the second wall portion. The window member is disposed on a top surface of the first wall portion and a top surface of the second wall portion and is inclined with respect to a mirror surface of the optical scanning device. In a cross-section parallel to the X-axis direction, the first wall portion is separated from a first line passing through a first end at a side of the first wall portion in the mirror surface and a first corner portion formed at the side of the first wall portion by an outer surface opposite to the frame member and a first side surface in the window member.

TECHNICAL FIELD

An aspect of the present disclosure relates to a mirror unit.

BACKGROUND

Japanese Unexamined Patent Publication No. 2017-215352 discloses amirror unit including an optical scanning device having a mirror surfaceprovided on a movable portion, a frame member disposed so as to surroundthe optical scanning device, and a flat window member covering anopening of the frame member. Light is incident to the mirror surfacethrough the window member from the outside, is reflected by the mirrorsurface, and is emitted to the outside through the window member.

SUMMARY

In the mirror unit described in Japanese Unexamined Patent PublicationNo. 2017-215352, a height of one of a pair of wall portions constitutingthe frame member and facing each other is formed to be higher than theother and the window member disposed on the frame member is inclinedwith respect to the mirror surface. When the window member is inclinedwith respect to the mirror surface, the traveling direction of the lightreflected by the window member can be different from the travelingdirection of the light reflected by the mirror surface and the lightreflected by the window member can be prevented from to be noise light.However, since the light reflected from the mirror surface isinterrupted by the higher portion in the wall portions constituting theframe member, there is concern that an optical scannable range by theoptical scanning device may be limited.

An object of an aspect of the present disclosure is to provide a mirrorunit capable of widening a scannable range by an optical scanning devicewhile reducing noise light.

A mirror unit according to an aspect of the present disclosure includes:an optical scanning device including a movable portion swingable arounda predetermined axis and a mirror surface provided on the movableportion; a frame member disposed so as to surround the mirror surfacewhen viewed from a first direction; and a window member formed in aplate shape and disposed on the frame member so as to cover an openingof the frame member, in which the frame member includes a first wallportion and a second wall portion which face each other in a seconddirection perpendicular to the first direction, in which a height of thefirst wall portion is higher than a height of the second wall portion,in which the window member is disposed on a top surface of the firstwall portion and a top surface of the second wall portion and isinclined with respect to the mirror surface, and in which in across-section passing through the mirror surface and parallel to boththe first direction and the second direction, the first wall portion isseparated from a first line passing through a first end at a side of thefirst wall portion in the mirror surface and a first corner portionformed at the side of the first wall portion by an outer surfaceopposite to the frame member and a first side surface in the windowmember.

In the mirror unit, the height of the first wall portion is higher thanthe height of the second wall portion and the window member is disposedon the top surface of the first wall portion and the top surface of thesecond wall portion and is inclined with respect to the mirror surface.Accordingly, the traveling direction of the light reflected by thewindow member can be different from the traveling direction of the lightreflected by the mirror surface and the light reflected by the windowmember can be prevented from to be noise light. Further, in thecross-section passing through the mirror surface and parallel to boththe first direction and the second direction, the first wall portion isseparated from the first line passing through the first end at a side ofthe first wall portion in the mirror surface and the first cornerportion formed at the side of the first wall portion by the outersurface opposite to the frame member and the first side surface in thewindow member. Accordingly, since it is possible to prevent the lightreflected from the mirror surface from being interrupted by the firstwall portion higher than the second wall portion, it is possible to usethe entire outer surface of the window member for optical scanning Thus,according to the mirror unit, it is possible to widen the scannablerange by the optical scanning device while reducing noise light.

The axis may be parallel to a third direction and the first wall portionmay be separated from the first line in a state in which the movableportion rotates to a maximum deflection angle around the axis. In thiscase, it is possible to further widen the scannable range by the opticalscanning device.

In the cross-section, the second wall portion may be separated from asecond line passing through a second end at the side of the second wallportion in the mirror surface and a second corner portion formed at theside of the second wall portion by the outer surface and a second sidesurface in the window member. In this case, it is possible to furtherwiden the scannable range by the optical scanning device.

A fillet may be formed at a boundary part between an inner side surfaceof the first wall portion and an inner surface at a side of the framemember in the window member by a bonding material between the first wallportion and the window member and in the cross-section, the fillet maybe separated from the first line. In this case, it is possible tofurther widen the scannable range by the optical scanning device.

A thickness of the window member may be thinner than a thickness of thefirst wall portion. In this case, it is possible to reduce the influenceof refraction on optical scanning in the window member.

According to an aspect of the present disclosure, it is possible toprovide a mirror unit capable of widening a scannable range by anoptical scanning device while reducing noise light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a mirror unit according to anembodiment.

FIG. 2 is a plan view of an optical scanning device.

FIG. 3 is a cross-sectional view of the mirror unit while a movableportion rotates.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure will be describedin detail with reference to the drawings. In the description below, thesame or corresponding components will be denoted by the same referencenumerals and redundant description will be omitted.

[Overall Configuration of Mirror Unit]

As illustrated in FIG. 1 , a mirror unit 100 includes an opticalscanning device 1 and a package 40 accommodating the optical scanningdevice 1. The package 40 includes a base 42, a frame member 43, and awindow member 44.

The base 42 is formed in a rectangular plate shape from, for example, anon-magnetic material such as aluminum nitride or aluminum oxide. Thebase 42 includes a main surface 42 a and a rear surface 42 b on the sideopposite to the main surface 42 a. The main surface 42 a is a surfaceconstituting a part of the inner surface of the package 40. The mainsurface 42 a is provided with a depression 42 c. A bottom surface of thedepression 42 c is provided with a depression 42 d. The optical scanningdevice 1 is disposed on the base 42, more specifically, a bottom surfaceof the depression 42 c. A magnetic field generating unit (notillustrated) which generates a magnetic field acting on a first drivecoil 11 and a second drive coil 12 of the optical scanning device 1 tobe described later is disposed on the side of the rear surface 42 b ofthe base 42. The magnetic field generating unit includes, for example,permanent magnets in a Halbach array.

The frame member 43 is disposed on the main surface 42 a so as tosurround the optical scanning device 1 (to surround a minor surface 7 ato be described later) when viewed from the Z-axis direction (the firstdirection) perpendicular to the main surface 42 a of the base 42. Theframe member 43 is formed in a rectangular frame shape from, forexample, a non-magnetic material such as aluminum nitride or aluminumoxide.

The window member 44 is configured by, for example, forming ananti-reflection film on both surfaces of a rectangular plate basematerial formed of a light-transmitting material such as glass. Thewindow member 44 is disposed on the frame member 43 so as to cover oneopening 43 a of the frame member 43 and faces the base 42 and theoptical scanning device 1 in the Z-axis direction. The window member 44is bonded to the frame member 43 by, for example, a bonding material 45such as low-melting glass so as to hermetically seal the opening 43 a.

The base 42 is bonded to the frame member 43 by, for example, a bondingmaterial 46 such as low-melting glass so as to hermetically seal theother opening 43 b of the frame member 43. Accordingly, the inside ofthe package 40 is hermetically sealed. The base 42 and the frame member43 may be integrally formed so as to configure a single member.

The bonding with the bonding materials 45 and 46 is not limited to thebonding with the low-melting glass and may be, for example, bonding withresin adhesive, low-temperature solder (Sn/Pb or Sn/Cu-based),low-temperature brazing material (Au/Sn alloy, Au/Ge alloy, or thelike), high-temperature brazing material (Ag-based or the like),projection welding, seam seal welding, laser welding, electron beamwelding, or the like.

[Configuration of Optical Scanning Device]

As illustrated in FIG. 2 , the optical scanning device 1 includes asupport portion 2 and a movable portion 10 which is swingable withrespect to the support portion 2. The movable portion 10 includes afirst movable portion 3, a second movable portion 4, a pair of firstconnection portions 5, a pair of second connection portions 6, and amirror 7. The support portion 2, the first movable portion 3, the secondmovable portion 4, the pair of first connection portions 5, and the pairof second connection portions 6 are integrally formed by, for example, aSilicon on Insulator (SOI) substrate. That is, the optical scanningdevice 1 is configured as a Micro Electro Mechanical Systems (MEMS)device.

The first movable portion 3 is formed in, for example, a rectangularplate shape. The second movable portion 4 is formed in, for example, arectangular ring shape so as to surround the first movable portion 3with a gap when viewed from an optical axis direction A. The supportportion 2 is formed in, for example, a rectangular ring shape so as tosurround the second movable portion 4 with a gap when viewed from theoptical axis direction A. That is, the support portion 2 is formed in aframe shape so as to surround the first movable portion 3 and the secondmovable portion 4 when viewed from the optical axis direction A.

The first movable portion 3 is connected to the second movable portion 4via the pair of first connection portions 5 so as to be swingable arounda first axis X1. That is, the first movable portion 3 is supported bythe support portion 2 so as to be swingable around the first axis X1.The first movable portion 3 includes a first portion 31 and a secondportion 32. The first portion 31 is formed in, for example, a circularshape when viewed from the optical axis direction A. The second portion32 is formed in, for example, a rectangular ring shape when viewed fromthe optical axis direction A. The first portion 31 is surrounded by thesecond portion 32 when viewed from the optical axis direction A and isconnected to the second portion 32 via a plurality of (in this example,two) connection portions 33. That is, gaps are formed between the firstportion 31 and the second portion 32 except for the plurality ofconnection portions 33.

The connection portion 33 is located, for example, at the center of twosides of the rectangular inner edge of the second portion 32intersecting a second axis X2. That is, in this example, the connectionportion 33 is located on the second axis X2. The first portion 31 may beconnected to the second portion 32 in a direction along at least thesecond axis X2.

The second movable portion 4 is connected to the support portion 2 viathe pair of second connection portions 6 so as to be swingable aroundthe second axis X2. That is, the second movable portion 4 is supportedby the support portion 2 so as to be swingable around the second axisX2. The first axis X1 and the second axis X2 are perpendicular to theoptical axis direction A and intersect each other (orthogonal to eachother in this example). The first portion 31 may be formed in arectangular shape or polygonal shape when viewed from the optical axisdirection A. The first portion 31 may be formed in a circular shape (forexample, an oval shape) when viewed from the optical axis direction A.The second portion 32 may be formed in a ring shape or a polygonal ringshape of a pentagon or more when viewed from the optical axis directionA.

The pair of first connection portions 5 are disposed on the first axisX1 so as to sandwich the first movable portion 3 in a gap between thesecond movable portion 4 and the second portion 32 of the first movableportion 3. Each first connection portion 5 functions as a torsion bar.The pair of second connection portions 6 is disposed on the second axisX2 so as to sandwich the second movable portion 4 in a gap between thesecond movable portion 4 and the support portion 2. Each secondconnection portion 6 functions as a torsion bar.

The mirror 7 is provided on the first portion 31 of the first movableportion 3. The mirror 7 is formed on the surface at the side opposite tothe base 42 (at the side of the window member 44) in the first portion31 so as to include an intersection point between the first axis X1 andthe second axis X2. For example, the mirror 7 is formed in a circular,oval, or rectangular film shape from a metal material such as aluminum,an aluminum-based alloy, gold, or silver. A surface at the side oppositeto the first movable portion 3 in the mirror 7 constitutes the mirrorsurface 7 a extending in a direction perpendicular to the optical axisdirection A. The center (geometric center, centroid) of the mirrorsurface 7 a matches the intersection between the first axis X1 and thesecond axis X2 when viewed from the optical axis direction A. In thisway, since the mirror 7 is provided on the first portion 31 connected tothe second portion 32 through the plurality of connection portions 33,deformation such as bending of the mirror 7 can be prevented even whenthe first movable portion 3 swings around the first axis X1 at theresonant frequency level.

The distance from the outer edge of the mirror surface 7 a to the outeredge of the first portion 31 is smaller than the width of the connectionportion 33. The width of the connection portion 33 is the length in adirection (in this example, a direction along the first axis X1)perpendicular to the extension direction of the connection portion 33(in this example, a direction along the second axis X2). The firstmovable portion 3 may not include the second portion 32 and theconnection portion 33. The distance from the outer edge of the mirrorsurface 7 a to the outer edge of the first portion 31 may be smallerthan the width of the second connection portion 6. The width of thesecond connection portion 6 is the length in a direction (in thisexample, a direction along the first axis X1) perpendicular to theextension direction of the second connection portion 6 (in this example,a direction along the second axis X2).

Further, the optical scanning device 1 includes a first drive coil 11, asecond drive coil 12, wirings 15 a and 15 b, wirings 16 a and 16 b,electrode pads 21 a and 21 b, and electrode pads 22 a and 22 b. In FIG.2 , for convenience of description, the first drive coil 11 and thesecond drive coil 12 are indicated by a one dotted chain line and thewirings 15 a and 15 b and the wirings 16 a and 16 b are indicated by asolid line.

The first drive coil 11 is provided in the second portion 32 of thefirst movable portion 3. The first drive coil 11 is wound a plurality oftimes in a spiral shape (a swirl shape) in a region outside the mirror 7(that is, the second portion 32) when viewed from the optical axisdirection A. A magnetic field generated by the magnetic field generatingunit acts on the first drive coil 11.

The first drive coil 11 is disposed in a groove formed on the surface ofthe first movable portion 3. That is, the first drive coil 11 is buriedin the first movable portion 3. One end of the first drive coil 11 isconnected to the electrode pad 21 a through the wiring 15 a. The wiring15 a extends from the first movable portion 3 to the support portion 2through one first connection portion 5, the second movable portion 4,and one second connection portion 6. For example, the wiring 15 a andthe electrode pad 21 a are integrally formed of a metal material such astungsten, aluminum, gold, silver, copper, or an aluminum-based alloy.

The other end of the first drive coil 11 is connected to the electrodepad 21 b through the wiring 15 b. The wiring 15 b extends from the firstmovable portion 3 to the support portion 2 through the other firstconnection portion 5, the second movable portion 4, and the other secondconnection portion 6. For example, the wiring 15 b and the electrode pad21 b are integrally formed of a metal material such as tungsten,aluminum, gold, silver, copper, or an aluminum-based alloy.

The second drive coil 12 is provided in the second movable portion 4.The second drive coil 12 is wound a plurality of times in a spiral shape(a swirl shape) in the second movable portion 4. A magnetic fieldgenerated by the magnetic field generating unit acts on the second drivecoil 12. The second drive coil 12 is disposed in a groove formed on thesurface of the second movable portion 4. That is, the second drive coil12 is buried in the second movable portion 4.

One end of the second drive coil 12 is connected to the electrode pad 22a through the wiring 16 a. The wiring 16 a extends from the secondmovable portion 4 to the support portion 2 through one second connectionportion 6. For example, the wiring 16 a and the electrode pad 22 a areintegrally formed of a metal material such as tungsten, aluminum, gold,silver, copper, or an aluminum-based alloy.

The other end of the second drive coil 12 is connected to the electrodepad 22 b through the wiring 16 b. The wiring 16 b extends from thesecond movable portion 4 to the support portion 2 through the othersecond connection portion 6. For example, the wiring 16 b and theelectrode pad 22 b are integrally formed of a metal material such astungsten, aluminum, gold, silver, copper, or an aluminum-based alloy.

Hereinafter, first to fifth examples will be described as an operationexample of the movable portion 10 of the optical scanning device 1. Inthe first example, a high-frequency drive current is applied to thefirst drive coil 11. At this time, since a magnetic field generated bythe magnetic field generating unit acts on the first drive coil 11, aLorentz force is generated in the first drive coil 11. Accordingly, thefirst movable portion 3 is swung around the first axis X1, for example,at the resonant frequency level.

Further, a drive current of a certain magnitude is applied to the seconddrive coil 12. At this time, since a magnetic field generated by themagnetic field generating unit acts on the second drive coil 12, aLorentz force is generated in the second drive coil 12. Accordingly, thesecond movable portion 4 is rotated around the second axis X2, forexample, in response to the magnitude of the drive current and isstopped at that state. Accordingly, according to the optical scanningdevice 1, light emitted from a predetermined light source can be scannedwhile being reflected by the mirror surface 7 a. Light is incident tothe minor surface 7 a through the window member 44 from the outside, isreflected by the mirror surface 7 a, and is emitted to the outsidethrough the window member 44. In the first example, the first movableportion 3 is swung at the resonant frequency and the second movableportion 4 is used statically.

In the second example, similarly to the operation of the first movableportion 3 of the first example, the first movable portion 3 is swung inresponse to the resonant frequency when a high-frequency drive currentis applied to the first drive coil 11 and the second movable portion 4is swung in response to the resonant frequency when a high-frequencydrive current is applied to the second drive coil 12. In this way, inthe second example, both the first movable portion 3 and the secondmovable portion 4 are swung at the resonant frequency.

In the third example, similarly to the operation of the second movableportion 4 of the first example, the first movable portion 3 is rotatedand stopped around the first axis X1 in response to the magnitude of thedrive current when a drive current of a certain magnitude is applied tothe first drive coil 11 and the second movable portion 4 is rotated andstopped around the second axis X2 in response to the magnitude of thedrive current when a drive current of a certain magnitude is applied tothe second drive coil 12. In this way, in the third example, both thefirst movable portion 3 and the second movable portion 4 are usedstatically.

In the fourth example and the fifth example, only the first movableportion 3 is driven. In the fourth example, since a high-frequency drivecurrent is applied to the first drive coil 11, the first movable portion3 is swung in response to the resonant frequency. In the fifth example,since a drive current of a certain magnitude is applied to the firstdrive coil 11, the first movable portion 3 is rotated and stopped aroundthe first axis X1 in response to the magnitude of the drive current. Thefourth example and the fifth example can be used, for example, in a casein which the second movable portion 4 is not provided or the like.

As described above, the optical scanning device 1 is disposed on thebase 42. The support portion 2 is fixed to the bottom surface of thedepression 42 c and the first movable portion 3 and the second movableportion 4 face the bottom surface of the depression 42 d. Since thedepression 42 d is provided, the first movable portion 3 and the secondmovable portion 4 can swing without interfering with the base 42.

[Configuration of Package]

As illustrated in FIGS. 1 and 3 , the frame member 43 includes a firstwall portion 51, a second wall portion 52, a third wall portion 53, anda fourth wall portion 54. Each of the wall portions 51 to 54 is formedin a plate shape and has the same thickness. The first wall portion 51and the second wall portion 52 extend in parallel to each other and faceeach other in the X-axis direction (the second direction) perpendicularto the Z-axis direction. The third wall portion 53 and the fourth wallportion 54 extend in parallel to each other and face each other in theY-axis direction (the third direction) perpendicular to both the Z-axisdirection and the X-axis direction. The third wall portion 53 isconnected to one end of the first wall portion 51 and one end of thesecond wall portion 52 and the fourth wall portion 54 is connected tothe other end of the first wall portion 51 and the other end of thesecond wall portion 52. The third wall portion 53 and the fourth wallportion 54 have, for example, the same shape.

A top surface 51 a at the side opposite to the base 42 in the first wallportion 51 is inclined with respect to the main surface 42 a so as tomove away from the main surface 42 a of the base 42 as it goes away fromthe second wall portion 52. A top surface 52 a at the side opposite tothe base 42 in the second wall portion 52 is inclined with respect tothe main surface 42 a so as to move away from the main surface 42 a ofthe base 42 as it goes toward the first wall portion 51. A height H1 ofthe first wall portion 51 is higher than a height H2 of the second wallportion 52. The height H1 of the first wall portion 51 is a maximumvalue of the distance from the main surface 42 a to the top surface 51 aand the height H2 of the second wall portion 52 is a maximum value fromthe main surface 42 a to the top surface 52 a.

A top surface 53 a at the side opposite to the base 42 in the third wallportion 53 is inclined with respect to the main surface 42 a so as tomove away from the main surface 42 a of the base 42 as it goes towardthe first wall portion 51 when viewed from the Y-axis direction. A topsurface 54 a at the side opposite to the base 42 in the fourth wallportion 54 is inclined with respect to the main surface 42 a so as tomove away from the main surface 42 a of the base 42 as it goes towardthe first wall portion 51 when viewed from the Y-axis direction.

The top surfaces 51 a to 54 a are flush with one other and located onthe same plane. The window member 44 is disposed on the top surfaces 51a to 54 a and is inclined with respect to the main surface 42 a (themirror surface 7 a) so as to move away from the main surface 42 a as itgoes from the second wall portion 52 toward the first wall portion 51.In other words, each of the top surfaces 51 a to 54 a is inclinedcorresponding to an angle of the inclination of the window member 44.

The first wall portion 51 may be formed by a plurality of portions.These portions may be formed separately with a gap providedtherebetween. In the embodiment, the entire top surface 51 a is formedflat, but the top surface 51 a may be divided into a plurality ofregions by forming a notch, a depression, a convex portion, or the likeon the top surface 51 a. The entire top surface 51 a does not need to beinclined at an angle corresponding to the inclination of the windowmember 44. For example, a line connecting two points in the top surface51 a may be inclined at an angle corresponding to the inclination of thewindow member 44. These matters are the same for the second wall portion52 to the fourth wall portion 54. The window member 44 may not be bondedto the frame member 43 in the entire top surfaces 51 a to 54 a and maybe boded to the frame member 43 in at least a part of the top surfaces51 a to 54 a.

The window member 44 includes an outer surface 44 a, an inner surface 44b, a first side surface 44 c, a second side surface 44 d, a third sidesurface, and a fourth side surface. The outer surface 44 a is a surfaceat the side opposite to the frame member 43 and the inner surface 44 bis a surface at the side of the frame member 43. The outer surface 44 aand the inner surface 44 b extend in parallel to each other. The firstside surface 44 c, the second side surface 44 d, the third side surface,and the fourth side surface extend in a direction perpendicular to theouter surface 44 a and the inner surface 44 b and are continuous to theouter surface 44 a and the inner surface 44 b. The window member 44 isdisposed on the frame member 43 so that the inner surface 44 b faces thetop surfaces 51 a to 54 a. The first side surface 44 c, the second sidesurface 44 d, the third side surface, and the fourth side surface arerespectively located on the top surface 51 a, the top surface 52 a, thetop surface 53 a, and the top surface 54 a.

The window member 44 includes a first corner portion 61 formed at theside of the first wall portion 51 by the outer surface 44 a and thefirst side surface 44 c and a second corner portion 62 formed at theside of the second wall portion 52 by the outer surface 44 a and thesecond side surface 44 d. When viewed from the Z-axis direction, thefirst corner portion 61 overlaps the top surface 51 a and the secondcorner portion 62 overlaps the top surface 52 a. A thickness T44 of thewindow member 44 is thinner than a thickness T51 of the first wallportion 51 and a thickness T52 of the second wall portion 52. In thisexample, the thickness T51 of the first wall portion 51 is the same asthe thickness T52 of the second wall portion 52. In this example, thefirst side surface 44 c is a flat surface, but the first side surface 44c may be a curved surface. In this case, the first corner portion 61 isformed at a boundary part between the flat outer surface 44 a and thecurved first side surface 44 c. Similarly, the second side surface 44 dmay be a curved surface. In this case, the second corner portion 62 isformed at a boundary part between the flat outer surface 44 a and thecurved second side surface 44 d.

A fillet 65 is formed at a boundary part between the inner side surface51 b of the first wall portion 51 and the inner surface 44 b of thewindow member 44 by a bonding material 45 between the first wall portion51 and the window member 44. A fillet 66 is formed in a boundary partbetween the inner side surface 52 b of the second wall portion 52 andthe inner surface 44 b of the window member 44 by a bonding material 45between the second wall portion 52 and the window member 44. The fillets65 and 66 are formed such that the bonding material 45 protrudes from agap between the frame member 43 and the window member 44 toward theinside of the package 40.

A positional relationship of the respective members will be describedwith reference to FIGS. 1 and 3 . The optical scanning device 1 isdisposed, for example, so that the first axis X1 is parallel to theX-axis direction and the second axis X2 is parallel to the Y-axisdirection. FIGS. 1 and 3 illustrate a cross-section parallel to both theX-axis direction and the Z-axis direction (a cross-section perpendicularto the Y-axis direction) and passing through the center of the minorsurface 7 a. Hereinafter, a positional relationship of respectivemembers in the cross-section will be described.

FIG. 1 illustrates a non-rotation state (a non-drive state and aninitial state) in which the movable portion 10 does not rotate aroundthe first axis X1 and the second axis X2. In the non-rotation state, thefirst movable portion 3 does not rotate around the first axis X1 and thesecond movable portion 4 does not rotate around the second axis X2. Inthe non-rotation state, the minor surface 7 a is parallel to the mainsurface 42 a of the base 42.

In the non-rotation state, the first wall portion 51 is separated from afirst line L1 passing through a first end P1 corresponding to an endportion at the side of the first wall portion 51 in the minor surface 7a and a vertex of the first corner portion 61. That is, the first lineL1 does not intersect the first wall portion 51. Further, in thenon-rotation state, the second wall portion 52 is separated from asecond line L2 passing through a second end P2 corresponding to an endportion at the side of the second wall portion 52 in the mirror surface7 a and a vertex of the second corner portion 62. That is, the secondline L2 does not intersect the second wall portion 52. Further, in thenon-rotation state, the fillet 65 is separated from the first line L1and the fillet 66 is separated from the second line L2. That is, thefirst line L1 does not intersect the fillet 65 and the second line L2does not intersect the fillet 66.

FIG. 3 illustrates a state in which the second movable portion 4 rotatesto the maximum deflection angle around the second axis X2. In thisstate, the first movable portion 3 does not rotate around the first axisX1. Also in the state illustrated in FIG. 3 , the first wall portion 51is separated from the first line L1 and the fillet 65 is separated fromthe first line L1. Further, the second wall portion 52 is separated fromthe second line L2 and the fillet 66 is separated from the second lineL2.

When the mirror surface 7 a is formed by mirror-finishing the surface ofthe first movable portion 3, the end portion of the mirror surface 7 ais the end portion of the processed region. Alternatively, when areflection film is not formed and the surface itself of the firstmovable portion 3 constitutes the mirror surface 7 a, the end portion ofthe mirror surface 7 a is the end portion of the first movable portion3. In the above-described embodiment, the first movable portion 3 isconnected to the first connection portion 5 in a cross-sectionperpendicular to the Y-axis direction and passing through the center ofthe mirror surface 7 a. In this case, the end portion of the firstmovable portion 3 is located at a boundary part between the firstmovable portion 3 and the first connection portion 5. As in theembodiment, when the first movable portion 3 includes the first portion31 and the second portion 32 surrounding the first portion 31 and theminor surface 7 a is provided on the first portion 31, the end portionof the minor surface 7 a is located in the vicinity of the end portionof the first portion 31.

[Function and Effect]

In the minor unit 100, the height H1 of the first wall portion 51 ishigher than the height H2 of the second wall portion 52 and the windowmember 44 is disposed on the top surface 51 a of the first wall portion51 and the top surface 52 a of the second wall portion 52 and isinclined with respect to the mirror surface 7 a. Accordingly, thetraveling direction of the light reflected by the window member 44 canbe different from the traveling direction of the light reflected by theminor surface 7 a and the light reflected by the window member 44 can beprevented from to be noise light. Further, in a cross-section parallelto both the X-axis direction and the Z-axis direction and passingthrough the minor surface 7 a, the first wall portion 51 is separatedfrom the first line L1 passing through the first end P1 at the side ofthe first wall portion 51 in the minor surface 7 a and the first cornerportion 61 formed at the side of the first wall portion 51 by the outersurface 44 a and the first side surface 44 c of the window member 44.Accordingly, since it is possible to prevent the light reflected fromthe minor surface 7 a from being interrupted by the first wall portion51 higher than the second wall portion 52, it is possible to use theentire outer surface 44 a of the window member 44 for optical scanningThus, according to the mirror unit 100, it is possible to widen thescannable range by the optical scanning device 1 while reducing noiselight.

In a state in which the movable portion 10 rotates to a maximumdeflection angle around the second axis X2, the first wall portion 51 isseparated from the first line L1. Accordingly, it is possible to furtherwiden the scannable range by the optical scanning device 1.

In the cross-section illustrated in FIG. 1 , the second wall portion 52is separated from the second line L2 passing through the second end P2at the side of the second wall portion 52 in the mirror surface 7 a andthe second corner portion 62 formed at the side of the second wallportion 52 by the outer surface 44 a and the second side surface 44 d ofthe window member 44. Accordingly, it is possible to further widen thescannable range by the optical scanning device 1.

In the cross-section illustrated in FIG. 1 , the fillet 65 is separatedfrom the first line L1. Accordingly, it is possible to further widen thescannable range by the optical scanning device 1.

The thickness T44 of the window member 44 is thinner than the thicknessT51 of the first wall portion 51. Accordingly, the effect of refractionat the window member 44 on optical scanning can be reduced. That is,although it is considered to separate the first corner portion 61 fromthe first wall portion 51 by thickening the window member 44 in order toseparate the first wall portion 51 from the first line L1, there isconcern that high-precision optical scanning cannot be realized sincethe refraction amount at the window member 44 increases when the windowmember 44 is formed to be thick. In contrast, in the minor unit 100,since the window member 44 is formed to be thin, the refraction amountat the window member 44 can be reduced and hence high-precision opticalscanning can be realized. Particularly, in the minor unit 100, it isextremely important to reduce the influence of refraction at the windowmember 44. This is because the incident angle of the light to the windowmember 44 increases depending on the angle of the mirror surface 7 a andthe refraction angle of the light emitted from the window member 44increases in the configuration in which light is scanned by swinging themovable portion 10 provided with the mirror surface 7 a as in the mirrorunit 100. Further, it is because the incident angle of the light to thewindow member 44 further increases in the configuration in which thewindow member 44 is inclined as in the mirror unit 100.

The first side surface 44 c of the window member 44 is inclined withrespect to the first wall portion 51 in the X-axis direction so as toface the location side of the second wall portion 52 (move closer to thesecond wall portion 52) as it goes away from the first wall portion 51when viewed from the Y-axis direction. Accordingly, the first cornerportion 61 at the side of the first wall portion 51 can be broughtcloser to the mirror surface 7 a in the X-axis direction. As a result,it is easy to separate the first line L1 from the first wall portion 51which is apt to interrupt light when the movable portion 10 is swungaround the second axis X2.

The present disclosure is not limited the above-described embodiment.For example, the materials and shapes of the components are not limitedto the materials and shapes described above and various materials andshapes can be adopted. The thickness T51 of the first wall portion 51may be different from the thickness T52 of the second wall portion 52.In the optical scanning device 1 of the embodiment, the movable portion10 is driven by an electromagnetic force, but the movable portion 10 maybe driven by an electrostatic force or a piezoelectric element. Theframe member 43 may be disposed on the support portion 2 so as tosurround the minor surface 7 a when viewed from the Z-axis direction.

The window member 44 may be provided with a notch. For example, thenotch may be formed in the outer surface 44 a and extend along the edgeportion of the outer surface 44 a. The notch may have, for example, arectangular cross-section. In this case, in the cross-section of FIG. 1, the window member 44 may have a first corner portion formed at theside of the first wall portion 51 by the outer surface 44 a and theinner surface of the notch, a second corner portion formed at the sideof the second wall portion 52 by the outer surface 44 a and the innersurface of the notch, a third corner portion formed by the inner surfaceof the notch and the first side surface 44 c, and a fourth cornerportion formed by the inner surface of the notch and the second sidesurface 44 d. In this case, in the cross-section of FIG. 1 , the firstwall portion 51 may be separated from the line passing through the firstend P1 at the side of the first wall portion 51 in the minor surface 7 aand the first corner portion. Accordingly, similarly to theabove-described embodiment, it is possible to prevent the lightreflected from the minor surface 7 a from being interrupted by the firstwall portion 51 higher than the second wall portion 52. In thecross-section of FIG. 1 , the second wall portion 52 may be separatedfrom the line passing through the second end P2 at the side of thesecond wall portion 52 in the minor surface 7 a and the second cornerportion. Accordingly, similarly to the above-described embodiment, it ispossible to further widen the scannable range by the optical scanningdevice 1. In the cross-section of FIG. 1 , the first wall portion 51 maybe separated or may not be separated from the line passing through thefirst end P1 and the third corner portion. In the cross-section of FIG.1 , the second wall portion 52 may be separated or may not be separatedfrom the line passing through the second end P2 and the fourth cornerportion. The outer surface 44 a of the window member 44 means a surfacelocated on the outermost side with respect to the optical scanningdevice 1 and does not include the inner surface of the notch.

What is claimed is:
 1. A minor unit comprising: a base including a main surface and a rear surface, an optical scanning device including a movable portion swingable around a predetermined axis and a minor surface provided on the movable portion, the optical scanning device being disposed on a side of the main surface with respect to the base, a frame member disposed on the side of the main surface with respect to the base so as to surround the minor surface when viewed from a first direction; and a window member attached to the frame member so as to cover an opening of the frame member, wherein the window member is inclined with respect to the mirror surface, wherein the main surface is provided with a first depression, wherein a bottom surface of the first depression is provided with a second depression, wherein the optical scanning device is disposed on the bottom surface of the first depression, and wherein at least part of the movable portion of the optical scanning device faces a bottom surface of the second depression.
 2. The minor unit according to claim 1, wherein the optical scanning device further includes a support portion supporting the movable portion so as to be swingable, and wherein the support portion is disposed on the bottom surface of the first depression.
 3. The mirror unit according to claim 2, wherein in the first direction, a thickness of the support portion of the optical scanning device is greater than a depth of the first depression.
 4. The mirror unit according to claim 2, wherein at least part of the support portion of the optical scanning device faces the bottom surface of the second depression.
 5. The mirror unit according to claim 1, wherein an entirety of the movable portion of the optical scanning device faces the bottom surface of the second depression.
 6. The mirror unit according to claim 1, wherein in the first direction, a depth of the second depression is greater than a depth of the first depression.
 7. The mirror unit according to claim 1, wherein in a state in which the movable portion rotates to a maximum deflection angle around the predetermined axis, the movable portion is not in contact with the bottom surface of the second depression.
 8. The mirror unit according to claim 1, wherein the frame member includes a first wall portion and a second wall portion which face each other in a second direction perpendicular to the first direction, wherein a height of the first wall portion is higher than a height of the second wall portion, and wherein in a cross-section passing through the mirror surface and parallel to both the first direction and the second direction, a width of the first depression in the second direction is greater than a width of the optical scanning device.
 9. The mirror unit according to claim 2, wherein the frame member includes a first wall portion and a second wall portion which face each other in a second direction perpendicular to the first direction, wherein a height of the first wall portion is higher than a height of the second wall portion, wherein when viewed from the first direction, the support portion is formed in a frame shape and includes a part disposed between the second wall portion and the movable portion, and wherein in a cross-section passing through the mirror surface and parallel to both the first direction and the second direction, a distance between the first depression and the second wall portion in the second direction is smaller than a width of the part of the support portion.
 10. The mirror unit according to claim 2, wherein the frame member includes a first wall portion and a second wall portion which face each other in a second direction perpendicular to the first direction, wherein a height of the first wall portion is higher than a height of the second wall portion, wherein when viewed from the first direction, the support portion is formed in a frame shape and includes a part disposed between the second wall portion and the movable portion, and wherein in a cross-section passing through the mirror surface and parallel to both the first direction and the second direction, a distance between the first depression and the second wall portion in the second direction is smaller than a distance between the part of the support portion and the movable portion in the second direction.
 11. The mirror unit according to claim 1, wherein the frame member includes a first wall portion and a second wall portion which face each other in a second direction perpendicular to the first direction, wherein a height of the first wall portion is higher than a height of the second wall portion, and wherein in a cross-section passing through the mirror surface and parallel to both the first direction and the second direction, a distance between the first depression and the second wall portion in the second direction is smaller than a width of the second wall portion.
 12. The mirror unit according to claim 1, wherein the frame member is disposed on the main surface of the base via a bonding material.
 13. The mirror unit according to claim 1, wherein the frame member and the base are integrally formed so as to form a single member. 